1. Field of the Invention
This invention relates to foam insulating products, particularly polyurethane and polyisocyanurate foams, containing carbon black as a filler and to a process for providing the insulating products.
2. Description of the Prior Art
The usefulness of foamed plastic materials in a variety of applications is well known. Rigid polyurethane and polyisocyanurate foams, for instance, are widely used as insulating structural members. It would be highly desirable to reduce the polymer content and concomitantly the cost of these members by the addition of fillers. The incorporation of fillers in the foam-forming reaction mixture has been repeatedly proposed in a general fashion in the prior art but little concrete evidence of such filler utilization has been described; see, for example, U.S. Pat. Nos. 3,644,168, 4,092,276, 4,110,270, 4,165,414, 4,248,975, 4,366,204, 4,467,014 and 4,649,162, and Canadian Pat. No. 853,771. This failure to broadly utilize fillers in rigid insulating foams is explainable because the advantages of adding the fillers have been perceived to be outweighed by the problems involved in incorporating them in the foam, maintaining the overall good foam quality, etc.
Japanese patent application, laid open as No. 57-147510, describes the use of carbon black in rigid foam plastics but reports k-factor reductions of less than 4% achieved with maximum carbon black levels under 0.7 weight percent. Nothing is disclosed in the application regarding the effect of aging on the k-factor of the filled foams. Although the degree of success reported in this Japanese application justifies little interest in carbon black as a filler for foams, it would be a considerable advance in the art to provide a filled, rigid foam characterized by reduced cost and a significantly improved insulating value.